154 
ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. 
[BULL. 168. 
5. LEADVILLE REGION. 
Rocks described by Cross in Mon. XII, Appendix A. Analyses 
made in the Denver laboratory. 
A. Porphyry, Mount Zion. Contains orthoclase, plagioclase, quartz, 
biotite, apatite, magnetite, and zircon. Analysis by L. G. Eakins. 
P. R. C. 504. 
B. White, or Leadville, porphyry. Contains orthoclase, plagio- 
clase, quartz, muscovite, magnetite, apatite, and zircon, with crystals 
which appear to be rutile and anatase. Sp. gr. 2.680, 16°. Analysis 
by W. F. Hillebrand. P. R. C. 587. 
C. Porphyry, summit of Mount Lincoln. Contains quartz, ortho- 
clase, plagioclase, biotite, apatite, sphene, magnetite, zircon, and 
allanite. The sample analyzed showed some muscovite, chlorite, and 
calcite. Sp. gr. 2.670, 16°. Analysis by W. F. Hillebrand. P. R. C. 
505. 
SiO, 
FeO. 
MgO 
CaO. 
Na.0 
K 2 0. 
H 2 0. 
Ti0 2 . 
p 2 o 5 - 
MnO 
SrO. 
BaO. 
Li 2 0. 
co 2 . 
CI... 
73.50 
14.87 
.95 
.42 
.29 
2.14 
3.46 
3.56 
.90 
none 
.03 
trace 
100. 12 
70.74 
14.68 
.69 
.58 
.28 
4.12 
2.29 
2.59 
2.09 
.06 
trace 
.03 
2.14 
trace 
100. 29 
c. 
66.45 
15.84 
2.59 
1.43 
1.21 
2.90 
3.92 
2.89 
.84 
.10 
.36 
.09 
.07 
trace 
1.35 
.05 
100. 09 
